Additives for increasing the separation yield of tall oil soap from black liquors

Abstract

Methods of increasing the yield of tall oil soap from a black liquor are provided. In an embodiment, the method comprises adding a separation aid to the black liquor. The separation aid comprises alkyl alcohol alkoxylates of formula RO[(CH 2 CHCH 3 O) x (CH 2 CH 2 O) y ]M and combinations thereof, wherein R is straight or branched alkyl of about 8 to about 22 carbon atoms; x is 1 to about 20; y is about 20 to about 80 and M is H or an alkali metal.

1. A method of recovering tall oil soap from a spent black liquor generated in the alkaline pulping of wood, the method comprising:
 adding to the spent black liquor during a black liquor recovery process which occurs subsequent to a Kraft process a separation aid selected from the group consisting of alkyl alcohol alkoxylates of formula RO[(CH 2 CHCH 3 O) x (CH 2 CH 2 O) y ]M and combinations thereof, wherein R is straight or branched alkyl of about 8 to about 22 carbon atoms; x is 1 to about 20; y is about 20 to about 80 and M is H or an alkali metal; and 
 separating the tall oil soap from the spent black liquor. 
 
     
     
       2. The method of  claim 1 , wherein M is H. 
     
     
       3. The method of  claim 1 , wherein M is K. 
     
     
       4. The method of  claim 1 , wherein R is straight or branched alkyl of about 16 carbon atoms. 
     
     
       5. The method of  claim 1 , wherein the alkyl alcohol alkoxylate is a block polymer. 
     
     
       6. The method of  claim 1 , wherein the concentration of the separation aid in the spent black liquor ranges from about 0.25 ppm to about 250 ppm. 
     
     
       7. The method of  claim 1 , wherein the concentration of the separation aid in the spent black liquor ranges from about 1.5 ppm to about 35 ppm. 
     
     
       8. The method of  claim 1 , wherein the separation aid is added to the spent black liquor as a component of an aqueous solution. 
     
     
       9. The method of  claim 1 , wherein the separating is done by a soap skimmer. 
     
     
       10. A method of generating tall oil fatty acids from a spent black liquor generated in the alkaline pulping of wood, the method comprising:
 adding to the spent black liquor during a black liquor recovery process which occurs subsequent to a Kraft process a separation aid selected from the group consisting of alkyl alcohol alkoxylates of formula RO[(CH 2 CHCH 3 O) x (CH 2 CH 2 O) y ]M and combinations thereof, wherein R is straight or branched alkyl of about 8 to about 22 carbon atoms; x is 1 to about 20; y is about 20 to about 80 and M is H or an alkali metal; 
 separating the tall oil soap from the spent black liquor; and 
 refining the tall oil soap into tall oil fatty acids. 
 
     
     
       11. The method of  claim 10 , wherein M is H. 
     
     
       12. The method of  claim 10 , wherein M is K. 
     
     
       13. The method of  claim 10 , wherein R is straight or branched alkyl of about 16 carbon atoms. 
     
     
       14. The method of  claim 10 , wherein the alkyl alcohol alkoxylate is a block polymer. 
     
     
       15. The method of  claim 10 , wherein the concentration of the separation aid in the spent black liquor ranges from about 0.25 ppm to about 250 ppm. 
     
     
       16. The method of  claim 10 , wherein the concentration of the separation aid in the spent black liquor ranges from about 1.5 ppm to about 35 ppm. 
     
     
       17. The method of  claim 10 , wherein the separating is performed by a soap skimmer. 
     
     
       18. The method of  claim 10 , wherein the refining is performed by a process selected from the group consisting of acidification, fractionation, distillation and combinations thereof. 
     
     
       19. A method of generating tall oil fatty acids, the method comprising:
 heating wood chips in a cooking liquor comprising sodium hydroxide and sodium sulfide to form a black liquor comprising wood pulp; 
 separating the wood pulp from the black liquor to form a spent black liquor; 
 adding to the spent black liquor during a black liquor recovery process which occurs subsequent to a Kraft process a separation aid selected from the group consisting of alkyl alcohol alkoxylates of formula RO[(CH 2 CHCH 3 O) x (CH 2 CH 2 O) y ]M and combinations thereof, wherein R is straight or branched alkyl of about 8 to about 22 carbon atoms; x is 1 to about 20; y is about 20 to about 80 and M is H or an alkali metal; 
 separating the tall oil soap from the spent black liquor; and 
 refining the tall oil soap into tall oil fatty acids. 
 
     
     
       20. The method of  claim 19 , wherein the refining is performed by a process selected from the group consisting of acidification, fractionation, distillation and combinations thereof.